Life Processes class 10 Notes

 

Life Processes class 10 Notes

Introduction:

        All living organisms need to perform certain basic activities to stay alive. These essential activities are known as life processes. They include nutrition, respiration, transportation, and excretion. Even the simplest living organisms carry out these processes to maintain their body structure, grow, repair damaged parts, and obtain energy for survival.

        The study of life processes helps us understand how plants and animals survive, how different organs work together, and how the body maintains balance. Knowledge of life processes is important not only for exams but also for understanding health, diseases, and the functioning of living beings.

       In this chapter, we will study in detail the different life processes such as nutrition, respiration, transportation, and excretion in plants and animals.

What are Life Processes? 

Definition

• Life processes are the basic vital activities performed by living organisms to maintain life, growth, and survival. 
• These processes are essential for carrying out all biological functions in plants and animals.

Why are Life Processes Necessary?

Life processes help organisms to:

• Obtain energy

• Grow and repair body parts

• Maintain internal balance (homeostasis)

• Remove harmful waste materials

• Survive in their environment

Without life processes, no organism can stay alive.

Nutrition

Definition

• Nutrition is the process by which an organism takes in food and utilizes it to obtain energy, grow, repair body tissues, and maintain life processes.

Why is Nutrition Necessary?

Nutrition is required to:

• Provide energy for life processes

• Help in growth and repair

• Maintain body functions

• Build immunity

Modes of Nutrition

There are two main modes of nutrition:

1. Autotrophic Nutrition

In this mode, organisms prepare their own food using simple inorganic substances.

Examples

• Green plants

• Algae

• Cyanobacteria

Process: Photosynthesis

Photosynthesis occurs in the presence of sunlight, chlorophyll, carbon dioxide, and water.

$$6CO_2 + 6H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2$$

Steps of Photosynthesis

1. Absorption of light energy by chlorophyll

2. Conversion of light energy into chemical energy

3. Reduction of CO₂ to carbohydrates

2. Heterotrophic Nutrition

In this mode, organisms depend on other organisms for food.

Types of Heterotrophic Nutrition

(a) Holozoic Nutrition

• Food is ingested, digested, absorbed, assimilated, and egested

• Example: Humans

Steps of Holozoic Nutrition

1. Ingestion:- (Ingestion is the process of taking food into the body through the mouth.)

2. Digestion:- (Digestion is the process by which complex food substances are broken down into simpler, soluble forms so that they can be absorbed by the body.)

3. Absorption:- (Absorption is the process by which digested food passes from the intestine into the blood through the walls of the small intestine.)

4. Assimilation:- (Assimilation is the process by which absorbed nutrients are utilized by body cells for energy, growth, repair, and maintenance.)

5. Egestion:- (Egestion is the process of removing undigested and unabsorbed food from the body through the anus.)

(b) Saprophytic Nutrition

• Organisms feed on dead and decaying matter

• Example: Fungi, bacteria

(c) Parasitic Nutrition

• Organisms live on or inside the host and take food

• Example: Tapeworm, Cuscuta

How do Organisms obtain their Nutrition?

• Different organisms have different digestive systems because the type of food and the method of obtaining it vary. 
• In simple, single-celled organisms, food can be taken in through the entire cell surface. 

Examples:-

1) Amoeba engulfs food using temporary finger-like structures to form a food vacuole where digestion occurs, and waste is later expelled.

2) Paramecium, food is taken in at a fixed spot, and cilia help move food towards it.

Nutrition in Human Beings

• Humans show holozoic nutrition, in which food is taken in solid form, digested, absorbed, assimilated, and the undigested part is removed from the body.

Steps of Nutrition in Human Beings

1. Ingestion

• Food is taken into the body through the mouth.

• Teeth help in chewing (mechanical digestion).

• Salivary glands secrete saliva containing salivary amylase, which begins digestion of starch.

2. Digestion

Digestion is the process of breaking down complex food into simpler, soluble substances.

(a) Mouth

• Saliva moistens food.

• Salivary amylase converts starch into sugar (maltose).

(b) Oesophagus

• Food is pushed towards the stomach by peristaltic movements.

• No digestion occurs here.

(c) Stomach

• Gastric glands secrete gastric juice, which contains:

  • Hydrochloric acid (HCl) – kills germs and provides acidic medium

  • Pepsin – digests proteins

  • Mucus – protects stomach lining

• Partial digestion of proteins occurs.

(d) Small Intestine

The small intestine is the main site of digestion and absorption.

• Receives:

  • Bile from liver (emulsifies fats)

  • Pancreatic juice (digests carbohydrates, proteins, and fats)

  • Intestinal juice (completes digestion)

• Digested food is absorbed by villi, which increase surface area.

(e) Large Intestine

• Absorbs water and salts

• Forms faeces

(f) Resctum

• The rectum is the final part of the large intestine where undigested food (faeces) is temporarily stored before being expelled from the body.

(g) Anus

• The anus is the opening at the end of the digestive tract through which faeces are expelled out of the body during the process of egestion.

3. Absorption

• Digested food passes into the bloodstream through the walls of the small intestine.

• Villi help in efficient absorption.

4. Assimilation

• Absorbed nutrients are carried by blood to body cells.

• Used for:

• Energy

• Growth

• Repair of tissues

5. Egestion

• Undigested food is removed through the anus.

Role of Associated Glands

• Salivary glands – secrete saliva

• Liver – produces bile

• Pancreas – produces digestive enzymes

Important Points for Exams

✔ Humans follow holozoic nutrition
✔ Small intestine is the main site of digestion and absorption
✔ Bile does not digest food but helps in fat digestion

Respiration

Definition:

• Respiration is the biochemical process by which food (glucose) is broken down in the presence or absence of oxygen to release energy required for life activities.
• In other words "Respiration is the process of oxidation of food to release energy for growth, repair, movement, and other life processes."

- Energy released is stored in the form of ATP (Adenosine Triphosphate).

Need for Respiration

Respiration is necessary to:

• Release energy for all life activities

• Carry out growth and repair

• Maintain body temperature

• Enable movement, circulation, and excretion

Types of Respiration

Respiration is of two types:

1) Aerobic Respiration

• Takes place in the presence of oxygen

• Occurs mainly in mitochondria

• Produces more energy

• End products: Carbon dioxide + Water

Equation:

$$\text{Glucose} + \text{Oxygen} \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{Energy (ATP)}$$

Example: Respiration in humans, plants, animals

2) Anaerobic Respiration

• Takes place in the absence of oxygen

• Produces less energy

• Occurs in yeast, bacteria, and muscle cells

In Yeast (Alcoholic fermentation):

$$\text{Glucose} \rightarrow \text{Alcohol} + \text{CO}_2 + \text{Energy}$$

In Human Muscles:

$$\text{Glucose} \rightarrow \text{Lactic Acid} + \text{Energy}$$

Note:- Lactic acid accumulation causes muscle cramps.

Differentiate between Aerobic and Anaerobic Respieation

Feature	Aerobic Respiration	Anaerobic Respiration
Oxygen	Required	Not required
Energy	More	Less
End products	CO₂ + H₂O	Alcohol / Lactic acid
Occurs in	Mitochondria	Cytoplasm

Respiration in Humans

Definition:

• Respiration in humans is the process by which oxygen is taken in, food is oxidised in body cells, and energy is released, while carbon dioxide is removed from the body.

- Energy released is stored in the form of ATP (Adenosine Triphosphate).

Steps of Respiration in Humans

Human respiration occurs in four main steps:

1. Breathing

2. Gaseous exchange

3. Transport of gases

4. Cellular respiration

1) Breathing

Breathing is a physical process involving:

• Inhalation – taking in oxygen-rich air

• Exhalation – releasing carbon dioxide-rich air

Human Respiratory System

The human respiratory system consists of the following organs:

1. Nostrils

Structure:

• Two external openings of the nose

• Lined with hair and mucus

Role / Function:

• Allow air to enter and leave the body

• Hair traps dust and microorganisms

• Prevents entry of large particles

2. Nasal Cavity

Structure:

• Hollow chamber behind nostrils

• Lined with mucus membrane and blood capillaries

Role / Function:

• Filters dust and germs

• Warms the incoming air

• Moistens the air before it reaches lungs

3. Pharynx

Structure:

• Muscular tube at the back of nasal cavity

• Common passage for air and food

Role / Function:

• Acts as a passage for air

• Directs air towards the larynx

4. Larynx (Voice Box)

Structure:

• Short cartilaginous tube

• Contains vocal cords

• Opening guarded by epiglottis

Role / Function:

• Produces sound

• Prevents food from entering trachea

• Allows air to pass into trachea

5. Trachea (Windpipe)

Structure:

• Long tube supported by C-shaped cartilage rings

• Lined with ciliated epithelium

Role / Function:

• Carries air from larynx to bronchi

• Cartilage prevents collapse

• Cilia remove dust particles

6. Bronchi

Structure:

• Trachea divides into two bronchi

• One bronchus enters each lung

Role / Function:

• Carry air into the lungs

• Further divide into bronchioles

7. Bronchioles

Structure:

• Fine, smaller branches of bronchi

• End in clusters of alveoli

Role / Function:

• Distribute air inside the lungs

• Control air flow to alveoli

8. Alveoli

Structure:

• Tiny, balloon-like air sacs

• Thin walls (one cell thick)

• Surrounded by capillary network

Role / Function:

• Site of exchange of gases

• Oxygen diffuses into blood

• Carbon dioxide diffuses out

• Provide large surface area

9. Lungs

Structure:

• Pair of spongy, elastic organs

• Enclosed in rib cage

• Covered by pleural membrane

Role / Function:

• Main organs of respiration

• Help in breathing and gas exchange

• Store inhaled air temporarily

10. Diaphragm

Structure:

• Dome-shaped muscular sheet

• Separates chest cavity from abdomen

Role / Function:

• Plays major role in breathing

• Contracts during inhalation

• Relaxes during exhalation

Summary of all Parts of Human Respiratory System:

Sr. No.	Organ	Function
1	Nostrils	Entry of air
2	Nasal cavity	Filters, warms, moistens air
3	Pharynx	Passage for air
4	Larynx	Voice Production
5	Trachea	Air Transport
6	Bronchi	Carry air to lungs
7	Bronchioles	Air distribution to lungs
8	Alveoli	Exchange of gases
9	Lungs	Main respiratory organs
10	Diaphragm	Helps in breathing movements

Mechanism of Breathing

1) Inhalation

• Diaphragm contracts and flattens

• Rib cage moves upwards and outwards

• Chest cavity volume increases

• Air enters lungs

2) Exhalation

• Diaphragm relaxes and becomes dome-shaped

• Rib cage moves downwards and inwards

• Chest cavity volume decreases

• Air moves out of lungs

Exchange of Gases

Definition:

Exchange of gases is the process in which:

• Oxygen (O₂) is taken into the blood

• Carbon dioxide (CO₂) is released from the blood

This exchange occurs between:

• Alveoli and blood in lungs

• Blood and body cells

Site of Exchange of Gases

• The exchange of gases takes place in the alveoli of the lungs.

Why alveoli are suitable for gas exchange?

• Very large surface area

• Thin walls (one cell thick)

• Surrounded by dense network of capillaries

• Moist surface for easy diffusion

Exchange of Gases in Lungs (Alveolar Exchange)

Process Involved: Diffusion

Diffusion is the movement of gases from higher concentration to lower concentration.

In Lungs:

• Oxygen concentration is higher in alveoli

• Oxygen diffuses into blood

• Carbon dioxide concentration is higher in blood

• Carbon dioxide diffuses into alveoli

Role of Haemoglobin

• Oxygen combines with haemoglobin in red blood cells

• Forms oxyhaemoglobin

• Helps in efficient transport of oxygen

Note:- This maintains concentration difference, allowing continuous diffusion.

Exchange of Gases in Tissues

• Oxygen concentration is higher in blood

• Oxygen diffuses into body cells

• Carbon dioxide produced by cells diffuses into blood

Mechanism of Exchange of Gases

Location	Oxygen	Carbon Dioxide
Alveoli → Blood	Enters blood	Leaves blood
Blood → Cells	Enters cells	Leaves cells

Factors Affecting Exchange of Gases

• Surface area of alveoli

• Thickness of alveolar walls

• Concentration difference

• Blood flow in capillaries

Importance of Exchange of Gases

• Supplies oxygen for cellular respiration

• Removes harmful carbon dioxide

• Maintains pH balance of blood

• Essential for survival

Transport of Gases

Definition:

Transport of gases is the process by which:

• Oxygen (O₂) taken from lungs is carried to all body cells

• Carbon dioxide (CO₂) produced in cells is carried back to the lungs

This transport is done by the blood circulatory system.

Transport of Oxygen

1. Role of Haemoglobin

• Oxygen is transported mainly by haemoglobin

• Haemoglobin is present in red blood cells (RBCs)

• It has a high affinity for oxygen

Formation of Oxyhaemoglobin

$$\text{Haemoglobin}+\text{Oxygen}\to \text{Oxyhaemoglobin}$$

• Occurs in lungs where oxygen concentration is high

• Oxyhaemoglobin carries oxygen to tissues

2. Release of Oxygen in Tissues

• Oxygen concentration is low in body tissues

• Oxyhaemoglobin breaks down

• Oxygen is released for cellular respiration

3. Small Amount of Oxygen

• A small amount of oxygen is dissolved directly in blood plasma

Transport of Carbon Dioxide

Carbon dioxide is transported from tissues to lungs in three forms:

1. As Bicarbonate Ions (Main Method)

• About 70% CO₂ is transported as bicarbonates

• CO₂ reacts with water to form carbonic acid

• Carbonic acid breaks into bicarbonate ions

2. Bound to Haemoglobin

• About 20–25% CO₂ binds with haemoglobin

• Forms carbaminohaemoglobin

3. Dissolved in Plasma

• About 5–10% CO₂ is dissolved directly in blood plasma

Transportation pathway summary:

Gas	From	To	Transported By
Oxygen	Lungs	Body cells	Haemoglobin
Carbon dioxide	Body cells	Lungs	Plasma & haemoglobin

Importance of Transport of Gases

• Supplies oxygen for energy production

• Removes carbon dioxide, a waste product

• Maintains proper pH of blood

• Essential for survival of cells

Link with Respiration

• Transport of gases connects lungs and cells

• Enables aerobic respiration

• Ensures continuous energy supply

Cellular Respiration

Definition:

• Cellular respiration is the process by which glucose is broken down inside cells to release energy in the form of ATP (Adenosine Triphosphate).

- It is the final and most important step of respiration.

Site of Cellular Respiration

• Aerobic respiration → occurs in mitochondria

• Anaerobic respiration → occurs in cytoplasm

Note:- Mitochondria are called the powerhouse of the cell.

Types of Cellular Respiration

Cellular respiration is of two types:

A. Aerobic Cellular Respiration

Definition:

Respiration that occurs in the presence of oxygen, producing maximum energy.

Equation:

$$\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon dioxide} + \text{Water} + \text{Energy (ATP)}$$

Steps (Brief):

1. Glucose is completely broken down

2. Oxygen helps in oxidation

3. Large amount of energy released

Energy Released:

• About 36–38 ATP molecules

B. Anaerobic Cellular Respiration

Definition:

Respiration that occurs in the absence of oxygen, producing less energy.

1. In Human Muscles

$$\text{Glucose} \rightarrow \text{Lactic Acid} + \text{Energy}$$

• Occurs during vigorous exercise

• Causes muscle cramps

2. In Yeast

$$\text{Glucose} \rightarrow \text{Alcohol} + \text{CO}_2 + \text{Energy}$$

• Known as fermentation

Role of ATP

• ATP is the energy currency of the cell

• Energy is stored in phosphate bonds

• Breaking ATP releases energy for:

• Movement

• Growth

• Repair

• Synthesis

Importance of Cellular Respiration

• Provides energy for all life processes
• Helps in growth and repair of tissues
• Maintains body temperature
• Essential for survival

Why Oxygen is Important?

• Oxygen helps in complete breakdown of glucose
• Releases maximum energy
• Prevents formation of harmful by-products

Anaerobic Respiration in Muscles

During heavy exercise:

• Oxygen supply becomes insufficient
• Muscles perform anaerobic respiration
• Glucose breaks down into lactic acid

$$\text{Glucose}\to \text{Lactic Acid}+\text{Energy}$$

Note: - Lactic acid causes muscle cramps and fatigue.

Difference Between Breathing and Respiration

Features	Breathing	Respiration
Process	Physical process	Chemical process
Takes place	Occurs in lungs	Occurs in cells
Energy	No energy released	Energy released
Involves	Involves air	Involves glucose

Transportation:

Definition:

• Transportation is the process by which food, oxygen, water, hormones, and waste materials are carried from one part of the body to another.

- All living organisms need an efficient transport system to maintain life processes.

Transportation in Human Beings

• Transportation in human beings is the process of carrying oxygen, digested food, hormones, and waste materials from one part of the body to another. This function is performed by the circulatory system.

Circulatory System

The human circulatory system consists of:

1. Heart

2. Blood

3. Blood vessels

1. Heart

Structure of Heart

• Muscular organ, roughly the size of a clenched fist

• Located slightly towards the left side of the chest

• Divided into four chambers:

  • Right atrium – receives deoxygenated blood

  • Right ventricle – pumps deoxygenated blood to lungs

  • Left atrium – receives oxygenated blood

  • Left ventricle – pumps oxygenated blood to the body

Valves in Heart

• Prevent backflow of blood

• Ensure blood flows in one direction only

Working of Heart

1. Deoxygenated blood from the body enters the right atrium

2. It moves to the right ventricle

3. From right ventricle, blood is sent to the lungs

4. Oxygenated blood returns to the left atrium

5. From left atrium, blood goes to the left ventricle

6. Left ventricle pumps blood to the entire body

Double Circulation

Definition

Blood passes through the heart twice in one complete cycle.

Types of Circulation

1. Pulmonary circulation

   • Heart → Lungs → Heart

   • Exchange of oxygen and carbon dioxide

2. Systemic circulation

   • Heart → Body → Heart

   • Supplies oxygen and nutrients to tissues

Importance

• Prevents mixing of oxygenated and deoxygenated blood

• Ensures efficient oxygen supply

• Supports high energy needs of humans

2. Blood

Components of Blood

a) Plasma

• Liquid part of blood

• Transports food, hormones, CO₂, and waste

b) Red Blood Cells (RBCs)

• Contain haemoglobin

• Transport oxygen

c) White Blood Cells (WBCs)

• Provide immunity

• Fight infections

d) Platelets

• Help in blood clotting

• Prevent excessive blood loss

3. Blood Vessels

Blood Vessel	Function	Special Feature
Arteries	Carry blood away from heart	Thick walls, high pressure
Veins	Carry blood towards heart	Valves present
Capillaries	Exchange materials	Very thin walls

Lymph (Tissue Fluid)

Definition

Lymph is a colourless fluid formed from plasma leaking out of capillaries.

Functions

• Transports fats absorbed from intestine

• Drains excess tissue fluid back to blood

• Plays role in immunity

Transport of Oxygen and Carbon Dioxide

• Oxygen binds with haemoglobin in RBCs

• Carbon dioxide is transported mainly in dissolved form

• Gas exchange occurs in alveoli of lungs

Transport of Nutrients and Waste

• Digested food carried by plasma

• Waste products transported to:

• Kidneys → urine

• Lungs → CO₂

• Skin → sweat

Transportation in Plants

• Transportation in plants is the process by which water, minerals, and food are carried from one part of the plant to another.

                    Since plants do not have a circulatory system like animals, they use specialised vascular tissues for transport.

Vascular Tissues in Plants

Plants have two types of vascular tissues:

1. Xylem

2. Phloem

1. Xylem

Function

• Transports water and dissolved minerals from roots to leaves and other parts of the plant.

• Movement is one-way (upward).

Components of Xylem

• Tracheids

• Vessels

• Xylem fibres

• Xylem parenchyma

(Most xylem cells are dead cells)

Mechanism of Water Transport in Plants

a) Root Pressure

• Water enters root hairs by osmosis

• Creates pressure that pushes water upward

b) Transpiration Pull

• Loss of water from leaves through stomata

• Creates a suction force that pulls water up through xylem

c) Cohesion and Adhesion

• Water molecules stick to each other (cohesion)

• Stick to xylem walls (adhesion)

• Helps in continuous upward movement of water

 Transpiration

Definition

Transpiration is the loss of water in the form of water vapour from aerial parts of the plant, mainly through stomata.

Importance of Transpiration

• Helps in upward movement of water

• Cools the plant

• Helps in absorption and transport of minerals

• Maintains cell turgidity

2. Phloem

Function

• Transports food (sugars) prepared in leaves to all parts of the plant.

• This process is called translocation.

• Movement is two-way (bidirectional).

Components of Phloem

• Sieve tubes

• Companion cells

• Phloem fibres

• Phloem parenchyma

(Phloem is mainly a living tissue)

Mechanism of Food Transport (Translocation)

• Food is prepared in leaves by photosynthesis

• Sugar is converted into sucrose

• ATP energy is used to load sugar into phloem

• Food is transported to growing and storage parts like:

• Roots

• Fruits

• Seeds

Difference between Xylem and Phloem

Xylem	Phloem
Transports water & minerals	Transports food
One-way movement	Two-way movement
Mostly dead cells	Mostly living cells
No energy required	Energy (ATP) required

Importance of Transportation in Plants

• Supplies water for photosynthesis
• Distributes food to all parts
• Maintains rigidity of plant body
• Supports growth and development

Excretion

• Excretion is the process of removal of metabolic waste products from the body. These wastes are harmful and must be eliminated to maintain internal balance (homeostasis).

Examples of Wastes

• Carbon dioxide
• Urea
• Excess water and salts

Excretion in Human Beings

Excretion in humans is carried out by the excretory system.

Parts of Human Excretory System

1. Kidneys

2. Ureters

3. Urinary bladder

4. Urethra

1. Kidneys

Structure

• Bean-shaped organs
• Located on either side of the backbone
• Each kidney contains nephrons (functional units)

Functions

• Filter blood
• Remove nitrogenous wastes
• Maintain water and salt balance

Nephron (Structural and Functional Unit of Kidney)

Parts of a Nephron

1. Bowman’s capsule

2. Glomerulus

3. Renal tubule

   • Proximal convoluted tubule (PCT)

   • Loop of Henle

   • Distal convoluted tubule (DCT)

4. Collecting duct

Working of Nephron (Urine Formation)

a) Ultrafiltration

• Blood is filtered in the glomerulus

• Water, urea, glucose, salts pass into Bowman’s capsule

b) Selective Reabsorption

• Useful substances like glucose, amino acids, water are reabsorbed into blood

c) Tubular Secretion

• Excess ions and wastes are secreted into the tubule

Urine Formation

• Urine contains:

  • Urea

  • Excess water

  • Salts

• Urine flows from:

• Kidney → Ureter → Urinary bladder → Urethra

Role of Other Organs in Excretion

Lungs

• Remove carbon dioxide and water vapour

Skin

• Sweat removes water, salts, and small amount of urea

Liver

• Converts toxic ammonia into urea

Dialysis (Artificial Kidney)

Definition

Dialysis is a process of removing wastes from blood when kidneys fail.

Importance

• Used for patients with kidney failure

• Uses a semi-permeable membrane

2. Ureters

• Ureters are thin, muscular tubes that form an important part of the human excretory system. Their main function is to carry urine from the kidneys to the urinary bladder.

Number and Location

• Humans have two ureters

• Each ureter arises from one kidney

• They extend from the renal pelvis of the kidney to the urinary bladder

Structure of Ureters

• Length: about 25–30 cm

• Narrow, elastic, muscular tubes

• Inner lining made of smooth muscle

• Connect kidney to urinary bladder

Function of Ureters

• Transport urine from kidneys to the urinary bladder

• Prevent backflow of urine

• Ensure continuous flow of urine

Mechanism of Urine Transport

• Urine is moved by peristaltic movements

• Peristalsis = rhythmic contraction and relaxation of muscles

• Does not depend on gravity

Role of Ureters in Excretion

• Act as passage pipes for urine

• Do not filter blood or form urine

• Help in proper elimination of metabolic wastes

3. Urinary Bladder

• The urinary bladder is a muscular, hollow organ of the human excretory system.
• Its main function is to temporarily store urine until it is excreted out of the body.

Location

• Present in the lower abdominal cavity

• Situated just behind the pubic bone

• Connected to the kidneys through two ureters

Structure of Urinary Bladder

• Bag-like, elastic structure

• Walls are made of smooth muscles

• Lined internally by stretchable epithelial tissue

• Can expand and contract according to the amount of urine

Capacity

• Can store about 300–500 mL of urine

• Stretching ability helps prevent continuous urination

Functions of Urinary Bladder

1. Temporary storage of urine

2. Controls the release of urine

3. Prevents leakage of urine

4. Helps in maintaining cleanliness and comfort

Mechanism of Urination (Micturition)

• When bladder fills, stretch receptors are activated

• Signals are sent to the brain

• Bladder muscles contract

• Sphincter muscles relax

• Urine is expelled through the urethra

Role in Excretion

• Does not filter blood

• Does not form urine

• Only stores and releases urine at appropriate time

4. Urethra

• The urethra is a thin muscular tube that forms the last part of the human excretory system.
• Its main function is to carry urine from the urinary bladder to the outside of the body.

Location

• Begins at the lower end of the urinary bladder

• Opens outside the body through the urinary opening

Structure of Urethra

• Narrow tube made of smooth muscles

• Lined with epithelial tissue

• Controlled by sphincter muscles

• Length varies in males and females (not required in detail for Class 10)

Function of Urethra

• Helps in expulsion of urine

• Controls the release of urine

• Prevents leakage of urine

Role in Urination (Micturition)

• When bladder is full:

  • Bladder muscles contract

  • Sphincter muscles relax

• Urine passes from bladder → urethra → outside

Important Exam Points

• Urethra is the final passage of urine

• It does not store urine

• It does not form urine

• Urination is a voluntary action controlled by brain

Difference Between Ureter and Urethra

Ureter	Urethra
Carries urine from kidney to bladder	Carries urine from bladder to outside
Two in number	One
Part of excretory pathway	Final passage of urine

Excretion in Plants

• Excretion in plants is the process of removal of waste materials produced during metabolic activities.
• Plants produce less toxic waste than animals and do not have a specialised excretory system.

Types of Wastes in Plants

• Oxygen (by-product of photosynthesis)

• Carbon dioxide (by-product of respiration)

• Excess water

• Resins, gums, latex

• Tannins and other metabolic wastes

Methods of Excretion in Plants

1. Diffusion

• Gaseous wastes like oxygen and carbon dioxide are removed by diffusion

• Occurs through:

• Stomata (leaves)

• Lenticels (woody stems)

2. Transpiration

• Excess water is removed in the form of water vapour

• Occurs mainly through stomata

• Helps in maintaining water balance

3. Storage of Wastes

Plants store waste products in:

• Leaves

• Bark

• Old xylem

• Fruits and seeds

These wastes are removed when these parts fall off.

4. Secretion of Substances

Some plants excrete wastes in the form of:

• Resins

• Gums

• Latex
  These substances are stored in special ducts and later removed.

5. Excretion Through Roots

• Some wastes are released into the surrounding soil

• Occurs through root cells

Excretion of Excess Oxygen

• Oxygen produced during photosynthesis is released into the atmosphere

• Occurs through stomata

Why Plants Do Not Need a Special Excretory System

• Produce less toxic wastes

• Many wastes are reused

• Wastes can be stored safely in plant tissues

• Removal occurs by diffusion and shedding of parts

Importance of Excretion in Plants

• Prevents accumulation of harmful substances

• Maintains internal balance

• Supports healthy growth

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